Jethro Mullen, CNN
The U.N. Security Council voted unanimously Thursday for tougher sanctions against North Korea.
China, North Korea's key ally, could have vetoed the resolution -- but instead agreed to it.
Leading up to the vote, Pyongyang unleashed an even harsher bout of fiery rhetoric than usual, threatening its enemies with the possibility of a "preemptive nuclear attack."
Despite the strong language, analysts say North Korea is still years away from having the technology necessary to mount a nuclear warhead on a missile and aim it accurately at a target.
The bellicose statement, carried by the North's state-run Korean Central News Agency, came during a week of high tension on the Korean Peninsula as military drills take place on either side of the heavily armed border that divides the two Koreas.
On Tuesday, North Korea said it planned to scrap the armistice that stopped the Korean War in 1953 and warned it could carry out strikes against the United States and South Korea.
In a new statement Thursday, a spokesman for the North Korean foreign ministry suggested the United States "is set to light a fuse for a nuclear war."
As a result, North Korea "will exercise the right to a preemptive nuclear attack to destroy the strongholds of the aggressors and to defend the supreme interests of the country," the statement said.
Analysts say North Korea is unlikely to seek a direct military conflict with the United States, preferring instead to try to gain traction through threats and the build up of its military deterrent.
South Korea had responded to Pyongyang's earlier saber-rattling with an unusually tough statement Wednesday, warning it would retaliate "strongly and sternly" against North's military command and forces if the "lives and safety of South Koreans" came under threat.
The menacing language from North Korea is consistent with the array of bellicose statements it has made previously -- it has declared the cease-fire to be irrelevant before.
But it comes amid increased concern over Pyongyang's dogged efforts to advance its nuclear and missile technology after a recent long-range rocket launch and underground atomic blast.
Doubts on effect of sanctions
The sanctions in the new resolution signal the latest attempt by the United States and its allies to hinder North Korea's weapons programs and pressure its young leader, Kim Jong Un, into taking a less confrontational approach.
But doubts remain over what difference the new measures will make.
Sanctions imposed after previous nuclear tests and rocket launches have failed to deter the North from its pursuit of a strong military deterrent that underpins its approach to foreign relations.
North Korea casts U.N. sanctions as part of an aggressive, U.S.-led conspiracy against it.
The goal of the new sanctions is to stymie the activities of North Korean banks and cash couriers who might be funneling money to the secretive regime's nuclear and missile programs.
The U.N. resolution also outlines measures to step up scrutiny of suspicious sea shipments and air cargo. And it expands restrictions to encompass several institutions and senior officials in the North's weapons industry, as well as a range of materials and technology known to be used in uranium enrichment.
China and and the United States, two of the permanent member of the Security Council, negotiated for weeks on the wording.
'Paying the price for ... a nuclear test'
Beijing's willingness to support additional sanctions was seen as an indication of its frustration with Pyongyang's decision to go ahead with the nuclear test last month despite Chinese urging not to do so.
"Kim Jong Un is now paying the price for going ahead with a nuclear test despite Chinese warnings not to create trouble during the political transition that has been under way in Beijing the past year," Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Programme at the UK-based International Institute for Strategic Studies, said this week.
"The real question, though, is the degree to which China will be willing to implement the U.N. sanctions and to impose punishment of its own," Fitzpatrick added, highlighting future levels of Chinese grain sales to North Korea as a possible indicator of Beijing's commitment to putting meaningful pressure on Pyongyang.
Analysts say Beijing wants to maintain the North as a buffer between its border and South Korea, a U.S. ally.
North Korea said the underground nuclear blast it conducted on February 12 was more powerful than its two previous detonations and used a smaller, lighter device, suggesting advances in its weapons program.
It was the first nuclear test the isolated state has carried out since Kim inherited power in December 2011 after the death of his father, Kim Jong Il, who made building up North Korea's military strength the focus of his 17-year rule.
The test followed the North's long-range rocket launch in December that succeeded in putting an object in orbit. Pyongyang insisted the launch had peaceful aims, but it was widely viewed as a test of ballistic missile technology.
The start this week of two months of joint U.S.-South Korean military exercises, known as Foal Eagle, has added to the simmering tensions.
North Korea has called the annual training exercises "an open declaration of a war," but South Korea says it notified Pyongyang that the drills "are defensive in nature."
Another joint exercise, Key Resolve, is scheduled to begin Monday, the day on which North Korea says its military will declare the 1953 armistice invalid.
On Thursday, came news that North Korea was conducting drills throughout its territory, with the South Korean defense ministry describing them as "unusually grand-scaled."
"We are tightening guard and stepping up readiness in case any unexpected or planned provocation happen from North Korea," said Kwon Ki Hyeon of the South Korean defense ministry.
North and South Korea have technically been at war for decades. The 1950-53 civil war ended in a truce rather than a peace treaty.
China supported the North with materiel and troops in the Korean War. The United States backed the South in the conflict, with soldiers from the two countries fighting side by side. About 28,500 U.S. soldiers are currently stationed in South Korea.
CNN's Elise Labott and Richard Roth contributed to this report.